1. Field of the Invention
The present invention relates to a ceramic substrate (hereinafter abbreviated as a ceramic) which can be utilized as the electronic material such as dielectric porcelain substrate, etc., and a circuit substrate by use of the ceramic and a method for preparing the ceramic.
2. Related Background Art
In the prior art, electronic circuit substrates have been formed only a conductive circuit, of a conductive circuit and resistance, or of a conductive circuit, resistance and a capacitor of a limited range, and other functional components are mounted separately as elements onto the substrate.
For example, in a porcelain substrate of the prior art, the substrate was primarily one having conductors being mounted by the soldering of a chip component, etc. onto the substrate. For this reason, miniaturization of the electronic circuit has been limited. FIG. 1 shows an example of the prior art. 111 is a porcelain substrate, 112 a conductor circuit, 113 a resistor and 114 a chip capacitor.
In recent years, attempts have been made to build in a plurality of capacitors within the substrate by varying the dielectric constants within the same porcelain substrate. However, it has been very difficult to form different dielectric portions within the same substrate, and a substrate having a plurality of capacitors built therein has not been realized or practically applied except under the present invention, because of, for example, the cumbersomeness of preparing a laminated ceramic capacitor. Also, it would be important to make the high dielectric constant portions sufficiently separated from each other such that different functional portions operate without influence from each other within a limited structural space.
Further, the problems of separate built-in functional portions in such an electronic component or circuit substrate is not limited to a single dielectric porcelain but they are universally exhibited when two or more of the same or different functional portions are to be formed within a ceramic substrate.